Introduction to Virology -...

Notes: Virology Read & Answer Questions from the following notes

into your ISN to study

1. Identify 3 things found in cells that are not in viruses.

2. Identify the 2 parts of a virus. 3. Name the 3 general groups of viruses. 4. Name the first virus discovered and who

discovered said virus. 5. How many different viral shapes are there? 6. Define virulence. 7. What is a bacteriophage?

Virus Notes Review Questions Glue in & Answer on paper. Get Teacher Stamp.

Viruses

Dead or alive?

First virus discovered Tobacco Mosaic Virus by Martinus Beijerinck – 1898 •Founder of Virology – even though he couldn’t see them! •Called them viruses after the Latin word – virulentus – poisonous or foul

Viral structure

• Viruses are NOT cells. • Basic Structure:

– Protein coat – Nucleic acid core (RNA or DNA) – Lipoprotein coat

• (second coat – only in enveloped viruses)

Virus Categories

• DNA viruses – stable, do not mutate rapidly – Single-stranded or double-stranded – Smallpox, Hepatitis B

• RNA viruses – mutate rapidly, unstable – Single-stranded or double-stranded – HIV, Rhinovirus

• At the boundary of life, between the macromolecules (which are not alive) and the prokaryotic cells (which are), lie the viruses and bacteriophages (phages).

• These twilight creatures are parasites responsible for causing many diseases in living things (herpes and HIV in humans, for example).

• Viruses are found everywhere.

• Viruses consist of a core of nucleic acid, either DNA or RNA, and a protective coat of protein molecules and sometimes lipids.

Viruses -The Boundary of Life

• In isolation, viruses and bacteriophages show none of the expected signs of life. They do not respond to stimuli, grow, or do any of the things we normally associate with life.

• Strictly speaking, they should not be considered "living" organisms at all.

• They are more complex than a lifeless collection of macromolecules and they do show one of the most important signs of life: the ability to reproduce at a fantastic rate but only in a host cell.

• Bacteriophages attack bacteria (prokaryotes)

• viruses attack eukaryotic cells.

• Viruses and bacteriophages invade cells and use the host cell's machinery to synthesize more of their own macromolecules.

• Once inside the host the bacteriophage or virus will either go into a Lytic Cycle -

destroying the host cell during reproduction.

OR • It will go into a Lysogenic Cycle - a parasitic type of partnership with

the cell

Lytic Cycle

• Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell.

• The viral nucleic acid takes over protein synthesis, creating new viruses.

• The host cell bursts, lyses, releasing the newly formed viruses.

• Host cell dies, hence the word lysis

Release

Before attachment

Attachment

Penetration and uncoating

Replication Assembly

The Lytic Cycle

The Lysogenic Cycle

Examples of LYSOGENIC viruses:

Varicella zoster AKA chicken pox – first enters lytic stage

after infecting a human– breakout of sores, then the lysogenic

cycle before travelling to the nervous system, where

it resides in the nerve fibers as an episomal element (element

residing in chromosome without affecting the cell). After a

long period of time(months to years) in a latent stage, the virus

is often reactivated to the lytic stage during which it manifests

itself as shingles.

Herpes – after the lysogenic phase, the lytic stage can damage

the nervous system in severe cases

Human Papilloma Virus – AKA warts

What triggers the lytic stage varies – stress, illness, immune

supressant disorders, etc.

A provirus is a DNA virus that has been inserted into a host cell chromosome.

A retrovirus injects the enzyme, reverse transcriptase into the cell to copy viral RNA into DNA.

• A virus is an obligate intracellular parasite containing genetic material surrounded by protein

• Virus particles can only be observed by an electron microscope

• The classification of viruses is based on the type of nucleic acid contained within – RNA viruses---also known as a retrovirus – DNA viruses

Group I - dsDNA viruses (double stranded DNA) Order Caudovirales (tailed bacteriophages).

Family Myoviridae - e.g. Enterobacteria phage T4 Family Podoviridae Family Siphoviridae - e.g. Enterobacteria phage λ

Unassigned Family Ascoviridae Family Adenoviridae Family Asfiviridae Family Baculoviridae Family Corticoviridae Family Fuselloviridae Family Guttaviridae Family Herpesviridae - e.g. Human herpseviruses Family Iridoviridae Family Lipothrixviridae Family Nimaviridae Family Papillomaviridae

Please DO NOT COPY these classification FAMILIES… COPY ONLY the GROUP INFO.

Group I - dsDNA viruses (double stranded DNA) Unassigned (cont’d)

Family Phycodnaviridae Family Plasmaviridae Family Polyomaviridae - e.g. Simian virus 40 Family Poxviridae - e.g. Cowpox virus, Variola virus (smallpox) Family Rudiviridae Family Tectiviridae Unassigned genera

Mimivirus; type species: Acanthamoeba polyphaga mimivirus

Please DO NOT COPY these classification FAMILIES… COPY ONLY the GROUP INFO.

Group II - ssDNA viruses (single stranded DNA) Unassigned bacteriophages

Family Inoviridae Family Microviridae

Unassigned viruses Family Geminiviridae Family Circoviridae Family Nanoviridae Family Parvoviridae - e.g. Parvovirus B19 (most depend on coinfection with adenoviruses for growth) Unassigned genera

Anellovirus ; type species: Torque teno virus

Please DO NOT COPY these classification FAMILIES… COPY ONLY the GROUP INFO.

Group III - dsRNA viruses (double stranded RNA) Family Birnaviridae Family Chrysoviridae Family Cystoviridae Family Hypoviridae Family Partitiviridae Family Reoviridae - e.g Rotavirus Family Totiviridae Unassigned genera

Endornavirus ; type species: Vicia faba endornavirus

Please DO NOT COPY these classification FAMILIES… COPY ONLY the GROUP INFO.

• Viral life cycle consists of six stages within the host cell 1. Attachment 2. Penetration 3. Uncoating 4. Multiplication 5. Assembly 6. Release

• Recognizing the shape, size, and structure of different viruses is critical to the study of disease – Viruses have an inner core of nucleic acid

surrounded by protein coat known as an envelope

– Most viruses range in sizes from 20 – 250 nanometers

Vaccines – named after Vaccinia – or Cow Pox

• Edward Jenner – 1796 -? – Small Pox

• Jonas Salk – 1952,1955 - ? - Polio

• Albert Sabin – 1962 – Oral polio vaccine

• Replication – Viruses replicate within a host cell while

utilizing the host cell’s nucleic acids.

• The cultivation of viruses is complex and includes three common methods – Chicken egg culture – Cell culture – Animal inoculation

http://www.cellsalive.com/phage.htm

Bacteriophage

http://learn.genetics.utah.edu/content/begin/cells/scale/

http://cbm.msoe.edu/includes/swf/HAAnimation.swf

http://www.npr.org/templates/story/story.php?storyId=114075029

Viral Replication

http://www.youtube.com/watch?v=RO8MP3wMvqg

“OUT” Question– EXIT TICKET Viruses

1. What was the most interesting virus you learned about today & Why?